(a) Technical Field
The present invention relates to a synchronizer hub for vehicles and a method for manufacturing the same, more particularly, a synchronizer hub which can reduce costs and improve mechanical properties by forming an inner spline and an outer spline of a transmission synchronizer hub for vehicles by using different materials.
(b) Description of the Related Art
In general, a vehicle includes a power transmission system that reduces power generated from an engine to transmit the power to the tires.
As illustrated in FIG. 1, a synchromesh mechanism of a manual transmission of the power transmission system includes a clutch hub 12 that is spline-connected to a shaft (not illustrated), a transmission gear 16 that is rotatably provided at the shaft, a sleeve 11 that is spline-connected to an outer circumference of the clutch hub 12, a clutch gear 16′ that is formed at a cone of the transmission gear 16 to mesh with the sleeve 11, a synchronizer ring 14 connected to the cone of the transmission gear 16 to perform a clutch operation upon coming in contact with the cone along with movement of the sleeve 11, and keys 15 that are inserted into grooves 12′ of the clutch hub 12 and are inserted into grooves of the synchronizer ring 14 along with the movement of the sleeve 11 while being pushed to an inner surface of the sleeve 11 by an extension force of a synchronizer spring (not illustrated). Accordingly, the sleeve meshes with the clutch gear of the transmission gear being rotated at a peripheral speed, and thus a rotational force of the transmission is transmitted to the shaft.
The synchronizer hub in the power transmission system serves to guide the sleeve so as to smoothly proceed during the transmission and to support the sleeve in a rotating direction.
Since the synchronizer hub has a complicated structure that includes a boss that causes friction with the clutch gear, a spline connection unit, an intermediate connection part, an outer spline part connected to the sleeve, the synchronizer hub is mostly made of a sintered material. Particularly, since sliding friction is caused between the boss and the clutch during the synchronization, a high-frequency heating process or an entire surface carburizing process is mostly performed on the boss in order to enhance wear resistance.
Unfortunately, a wear resistance process of the boss may result in an increased product cost. In recent years, as transmission torque is increased, when stiffness of the sintered material reaches a limit, the synchronizer hub may be damaged.
In order to solve the above-described problems, Korean Patent Application Publication No. 2010-5358 discloses a low-cost synchronizer hub having high strength by sintering and control-cooling a ferritic powder which is an alloy of chrome and molybdenum. However, the synchronizer hub having such a structure is not easily manufactured, and durability thereof is not satisfactory.
In addition, Korean Patent No. 10-217604 discloses a double structure of a synchronizer that is separately formed as a double structure of an internal insertion part made of a copper powder sintered material and an outer ring body made of a sintered alloy material, and in which the internal insertion part is integrally formed with the outer ring body by being forcibly inserted into the outer ring body. However, in this case, the number of components is increased. Further, in the synchronizer, since an outer ring is forcibly inserted, there is a higher possibility of product failure.
Meanwhile, as a technology that manufactures a body of one molded product by using different kinds of metals, Japanese Patent Application Publication No. 1996-41503 discloses a technology in which a first powder material is temporarily compacted to mold a first temporary compaction powder material, a second powder material is filled in a mold frame into which the first temporary compaction powder material is inserted, the second compact powder material is temporarily compacted to mold a second temporary compaction powder material, the first temporary compaction powder material and the second temporary compaction powder material are integrally pressed to mold a compaction powder molded object, and then the compaction powder molded object is sintered. Moreover, Korean Patent Application Publication No. 2011-117831 discloses a technology of forming a cutting tip using different materials by pressing hard metal powders to form a cutting tip, pressing soft metal powders to form a cutting block, and then press-molding the cutting tip and the cutting block to be combined with each other.
However, in the technology using different materials, it is difficult to select and to form a metal material depending on a function and kind of a molded product to which the technology is applied, and it is difficult to integrate different materials. In addition, it is difficult to maintain the molded product to have excellent mechanical properties, and particularly, it may be difficult to apply the technology due to a structural characteristic of a synchronizer hub for vehicles.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.